Some systems that amplify high-bandwidth signals use a first power converter circuit (typically a switch-mode boost power converter) to boost a DC voltage up to a fixed high-voltage rail. The fixed high-voltage rail is used as an input voltage to a second power converter circuit. The second power converter circuit is suitable for amplifying time-varying signals which have a high maximum frequency component or signal bandwidth. The second power converter is often realized as a linear power converter circuit, and in some cases, as a switch-mode buck converter circuit. In such embodiments, the second power converter circuit receives the time-varying signal and steps down the input voltage of the fixed high-voltage rail to generate an amplified form of the time-varying signal.
In instances where the second power converter circuit is a switch-mode buck converter, a time-varying output signal of the switch-mode buck converter relates linearly to the fixed input voltage of the buck converter as a function of a switching signal duty-cycle. Because of this linear relationship, the switch-mode buck converter can be implemented without a feedback loop, thereby increasing the signal bandwidth of the second power converter circuit. By contrast, the first power converter circuit, when implemented as a switch-mode boost power converter, has a non-linear relationship between its output voltage as a function of a duty-cycle of a switching signal. Because of this non-linear relationship, the typical switch-mode boost power converter circuit typically cannot be configured without a feedback loop.